The present invention relates to a lawn and garden tractor and more specifically relates to electric circuitry for ensuring safe and proper operation of a lawn and garden tractor.
The hazards attendant with starting a tractor having its transmission or power take-off engaged and in operating a tractor with its parking brake engaged have long been recognized. Various electrical interlock systems have been devised to avoid unsafe starting conditions (for example, see U.S. Pat. No. 3,736,729 granted to Peterson on June 5, 1973 and U.S. Pat. No. 3,782,084 granted to Harkness on Jan. 1, 1974) and various mechanical interlock systems have been devised to avoid a tractor from being operated with its park brake seet (for example, see U.S. Patent application Ser. No. 604,166 filed Aug. 13, 1975 by Welck and having the same assignee as does this case).
The electrical interlock system of the above-identified patents are not entirely satisfactory since they are grounding circuits which must be completed in order to disable the starting of the tractor. Thus, even if an unsafe condition exists, a broken electrical conductor or corroded switch contacts may open the circuit and permit starting.
The mechanical interlock of the above-identified patent application suffers from the disadvantage of being relatively expensive to fabricate since it consists of linkage including levers, rods, stops and biasing springs.